Abstract
Reactive compounding of terminally phenolic OH-functionalized polycarbonate (PC) with epoxy-functionalized polymethylmethacrylate (PMMA) prepared by copolymerization with glycidyl methacrylate was investigated. It was spectroscopically demonstrated that a PC/PMMA copolymer was formed during the melt reaction of the functional groups. Zirconium acetylacetonate could catalytically accelerate this reaction. Correlations of the phenomenological (optical and mechanical) properties with the molecular level and mesoscopic (morphological) structure were discussed. By the investigated reactive compounding process, transparent PC/PMMA blends with two-phase morphologies were obtained in a continuous twin-screw extruder, which, for the first time, combined the high transmission of visible light with excellent mechanical performance (e.g., synergistically improved tensile and flexural strength and high scratch resistance). The transparency strongly depended on (a) the degree of functionalization in both PC and PMMA, (b) the presence of the catalyst, and (c) the residence time of the compounding process. The in-situ-formed PC/PMMA copolymer influenced the observed macroscopic properties by (a) a decrease in the interphase tension, leading to improved and stabilized phase dispersion, (b) the formation of a continuous gradient of the polymer composition and thus of the optical refractive indices in a diffuse mesoscopic interphase layer separating the PC and PMMA phases, and (c) an increase in the phase adhesion between PC and PMMA due to mechanical polymer chain entanglement in this interphase.
Highlights
Further synergistic effects are observed in the case of the reactively compounded blends based on m-PMMA8, independently of whether zirconium (IV) acetylacetonate (ZrAcac) was applied as a catalyst, for the values of ultimate strength σfN measured for the materials in both tensile and flexural tests
Transparent PC/PMMA blends with significantly enhanced tensile/bending performance and scratch resistance could be obtained via the reactive extrusion of terminally phenolic hydroxyl (pOH)-functionalized PC with statistical glycidyl methacrylate (GMA)/methyl methacrylate (MMA) copolymers
Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy that the process results in the in-situ formation of PC/PMMA
Summary
All PC materials were obtained from Covestro Deutschland AG (Leverkusen, Germany) Both non-modified PC grades are commercial products. The pOH contents of the modified PC grades m-PC* and m-PC**, on the other hand, in both cases, correspond approximately to a level of 70 ± 5 mol% of the polymer end groups. Due to the higher molecular weight of the SAG8 compared to m-PMMA8, this, corresponded to a larger average EP functionality per polymer chain of 32 in the SAG8. For the fundamental investigation of the melt reaction kinetics of EP-containing polymers (see Section 2.2.1), 4-cumylphenol (CP), 1,1-diphenylethanol, diphenylmethanol, 1-naphthalenemethanol, and diphenyl carbonate were used as model compounds to study reactivity with pOH, tertiary (tert.), secondary (sec.), and primary (prim.) aliphatic (a)OH and carbonate functional groups, respectively. Catalyst p-toluene sulfonic acid monohydrate (p-TSA) was sourced from Merck KGaA (Darmstadt, Germany)
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